Elbow prosthesis

ABSTRACT

A humeral component, forming a first articulating surface, and an ulnar component forming a second articulating surface adapted to be disposed around a part of the first articulating surface and to pivot about its longitudinal axis. This ulnar component is provided with structure for mounting a locking element which forms a third articulating surface extending the second and adapted likewise to be disposed around a part of the first surface. These mounting structure comprise guiding structures adapted to cooperate with complementary structure provided on the locking element in order to guide this element in translation with respect to the ulnar component, up to a position where blocking structure provided respectively on the locking element and on the ulnar component may be employed to immobilize this element on this component, these blocking structure being able to be employed only in this position.

This application claims the benefit of U.S. provisional application No.60/473,446 filed May 28, 2003.

FIELD OF THE INVENTION

The present invention relates to an elbow prosthesis comprising at leastone humeral component and one ulnar component.

It concerns more particularly an elbow prosthesis of which the ulnarcomponent is adapted to receive a locking element which forms anarticulating surface extending that of the ulnar component, thearticulating surfaces of the locking element and of the ulnar componentbeing adapted to be arranged together around at least a part of anotherarticulating surface belonging to a humeral component. A prosthesis ofthis type is known from EP-A-1 051 954.

BACKGROUND OF THE INVENTION

In such a prosthesis, the locking element is maintained in position onthe ulnar component thanks to a screw introduced in a through housing inthis element and tightened in a tapping provided on the ulnar component.It has proved in practice that the positioning of the locking element onthe ulnar component is not always optimum when such a screw istightened, which may lead to a skewed positioning of the screw withrespect to the tapping, to such a point that the thread of the screw orthe tapping may be distorted, thus preventing the locking element frombeing mounted. In addition, the afore-mentioned screw serves both tobring the locking element into correct position with respect to theulnar component and to ensure blocking of these two elements withrespect to each other. As a result, such an ulnar component must mostoften be fitted while the articulation of the elbow is in maximumflexion, which renders the surgeon's work more complex. It even happensthat such fitting in maximum flexion is not possible, particularly inthe case of marked obesity of the patient.

It is a more particular object of the invention to overcome thesedrawbacks by proposing an elbow prosthesis whose fit is facilitated,when it comprises a locking element as mentioned hereinabove.

SUMMARY OF THE INVENTION

To that end, the present invention relates to an elbow prosthesiscomprising a humeral component, forming a first articulating surface,and an ulnar component forming a second articulating face adapted to bedisposed around a part of the first articulating surface and to pivotabout a longitudinal axis of this surface, the ulnar component beingprovided with means for mounting a locking element which forms a thirdarticulating surface extending the second articulating surface andadapted likewise to be disposed around a part of the first articulatingsurface. This prosthesis is characterized in that the afore-mentionedmounting means comprise guiding means adapted to cooperate withcomplementary means provided on the locking element in order to guidethis element in translation with respect to the ulnar component, up to aposition where blocking means provided respectively on the lockingelement and on the ulnar component may be employed to immobilize thelocking element on the ulnar component, these blocking means being ableto be employed only in this position.

Thanks to the invention, the guiding means ensure an adequatepositioning of the locking element with respect to the ulnar componentbefore the blocking means are employed to effect an efficientimmobilization of the locking element with respect to the ulnarcomponent. In other words, the blocking means do not serve to bring thelocking element in a configuration allowing its blocking, this functionbeing performed by the guiding means which may be positioned andconfigured to ensure this function best.

In addition, an elbow prosthesis may incorporate one or more of thefollowing characteristics, taken in any technically admissiblecombination:

The blocking means comprise a screw and a complementary tapping providedrespectively on the locking element and on the ulnar component, or viceversa, the direction of relative translation between the locking elementand the ulnar component as imposed by the guiding means beingnon-parallel to the longitudinal axis of the tapping and/or of theafore-mentioned screw.

The guiding means comprise at least one element in relief projectingwith respect to a principal part of the ulnar component, while thecomplementary means provided on the locking element are adapted tointeract with this element in relief by cooperation of shapes. In thatcase, the aforementioned element in relief may be a nose, while thecomplementary means comprise a fork of which two branches definetherebetween a volume for receiving and for slide of this nose.

The guiding means and the blocking means are arranged in the vicinity oftwo opposite edges of the second articulating surface of the ulnarcomponent, while the complementary means and the blocking means providedon the locking element are arranged on two opposite edges of thatelement.

The blocking means comprise a screw and a tapping, which arecomplementary and respectively provided on the locking element and onthe ulnar component, or vice versa, while means are provided forblocking this screw in rotation. The head of the screw may thus be ofnon-circular section, while the piece against which this head bearsforms a space for receiving this head, with contact between the surfaceof this piece and the outer surface of the head. More particularly, thehead of the screw may be provided with catch elements adapted topenetrate superficially in the surface of the afore-mentioned piece. Ina variant, the piece against which the head of the screw bears may beprovided with a tab foldable into configuration of blockage of thishead. In that case, the head of the screw may be of polygonal profile,with faces whose width is greater than the width of the foldable tab.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood and other advantagesthereof will appear more clearly in the light of the followingdescription of a form of embodiment of a prosthesis in accordance withits principle, given solely by way of example and made with reference tothe accompanying drawings, in which:

FIG. 1 is an exploded view in perspective of an elbow prosthesisaccording to the invention.

FIG. 2 is a longitudinal section of the ulnar component and of thelocking element in the course of assembly.

FIG. 3 is a section similar to FIG. 2 while the locking element ismounted on the ulnar component.

FIG. 4 is a view in perspective of the metal part of the ulnarcomponent.

FIG. 5 is a section along line V-V of FIG. 3 and

FIG. 6 is a view in perspective of the ulnar component and of thelocking element of the prosthesis, on a larger scale.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings, the prosthesis visible in FIGS. 1 to 3comprises a humeral component 10 comprising a stem 11 intended to bedriven in the medullary canal of a humerus H and extending in twobranches 12 and 13, each pierced with an orifice 12a, 13a for passage ofa hollow screw 14 forming pin. The hollow nature of the screw 14 allowsthe passage of suture yarns. The orifice 12a is tapped, allowing thescrew 14 to be screwed. The stem 11 also extends in a third branch 15intended to come into abutment against the cortex of the humerus.

An elongated piece 16 is provided with a central bore 16a whosedimensions are such as to receive the screw 14, this making it possibleto mount the piece 16 between the branches 12 and 13. The piece 16 isprovided with two end surfaces 16b and 16c provided to come respectivelyinto contact with the opposite surfaces of the branches 12 and 13.

Between the surfaces 16b and 16c, the piece 16 is substantiallycylindrical, with circular base, and forms a surface of articulation S₁which is also substantially cylindrical, whose generatrix G₁ is curvedand concave, in that the diameter of the surface S₁ is minimum in thecentral part of the piece 16 included between the surfaces 16b and 16c.X₁ denotes the axis of symmetry of the surface S₁.

The piece 16 extends in an extension 16d whose outer surface S₄ isconvex and which covers the branch 12 when the piece 16 is mountedbetween the branches 12 and 13.

The whole of the humeral component 10 is made of metal.

The ulnar component 20 comprises a metal stem 21 intended to be insertedin the medullary canal of the ulna C and which is in one piece with abranch 22 likewise made of metal, of concave shape and whose innersurface is covered with a lining 23 made of a material adapted to thefriction with the metal piece 16, for example polyethylene. The lining23 is mounted on the branch 22 by cooperation of shapes. A pin 27 makesit possible to immobilize elements 22 and 23 with respect to each other.

The inner surface of the lining 23 forms a surface of articulation S₂whose shape is complementary to that of surface S₁. X₂ denotes thecentral axis of elements 22 and 23.

The respective diameters of surfaces S₁ and S₂, which diameters arevariable along axes X₁ and X₂, are chosen so that the surface S₂ may bedisposed around the surface S₁, with a slight clearance, this allowing arotation of the components 10 and 20 with respect to each other aboutaxes X₁ and X₂ which, in that case, merge.

Moreover, the profiles of the generatrices of surfaces S₁ and S₂ arechosen so as to allow a degree of mobility of the surface S₁ in surfaceS₂, in the sense of varus-valgus, i.e. about an axis perpendicular to X₁and X₂.

A locking element 30 is intended to be mounted on the component 20 andcomprises a metal casing 32 and a lining 33 immobilized with respect toeach other by clipping. The lining 33 is advantageously made of the samematerial as the lining 23 and forms a concave articulating surface S₃intended to extend the surface S₂ and, with it, surround the surface S₁.

In order to facilitate assembly of the element 30 on the component 20,this component is provided, in extension of the outer surface 24 of thebranch 22, with an element in relief 25 in the form of a nose or beakwhich projects beyond the part 22a of the branch 22 covered by thelining 23.

Furthermore, the casing 32 of the element 30 extends beyond its part 32acovered by the lining 33, in an extension in the form of a fork 35 ofwhich the two branches 35a and 35b together define a volume 35c forslide and reception of the nose 25 when the element 30 is mounted on thecomponent 20.

The nose 25 is disposed in a space 23c defined by the lining 23 whichextends beyond the part 22a of the branch 22 that it covers. In its part23d which extends in overhang with respect to the part 22a, the lininghas a substantially U-shaped cross-section. The space 23c is defined atthe centre of this U.

The nose 25 has a width decreasing in the direction of the bottom of theU formed by the part 23d. In this way, the sides 25a and 25b of the nose25 diverge, moving away from this bottom and approaching the branches ofthe U formed by the part 23d. The nose 25 has a section substantially inthe form of a dove-tail.

In addition, grooves 25c and 25d are formed on either side of the nose25. These grooves have profiles allowing them to receive convex parts35d and 35e of the branches 35a and 35b.

The branches 35a and 35b thus have a geometry compatible with theirintroduction in the space 23c, on either side of the nose 25. Theirsurfaces intended to face towards the nose 25 deviate from each othertowards the outside of the element 30, with the result that thesesurfaces are substantially parallel to sides 25a and 25b.

In this way, the direction of assembly of the element 30 on thecomponent 20 is necessarily that indicated by arrow F₁ in FIG. 2, thisdirection being imposed by the cooperation of shapes between the nose 25and the fork 35. In effect, as indicated hereinabove, the transversesections of the nose 25 on the one hand and of the inner parts of thebranches 35 are chosen to impose this direction of slide.

Furthermore, the component 20 is provided with a tapping 26 forreceiving a screw 36 which traverses a through housing 37 provided tothat end in the element 30.

The tapping 26 and the housing 37 are configured so that they arealigned, in a direction Y₁ perpendicular to axis X₂, at the end of theslide of the element 30 with respect to the component 20. Such slidetakes place until the linings 23 and 33 come into abutment against eachother in the vicinity of the members 25 and 35, as shown in FIG. 3. Itis then possible to screw the screw 36 in the tapping 26, in thedirection of arrow F₂ in FIGS. 2 and 3. In the configuration of FIG. 3,the central axes of the screw 36 and of the tapping 26 merge and areparallel to direction Y₁.

The direction Y₁ is not parallel to the direction of displacement of theelement 30 with respect to the component 20 during its assembly, i.e. toarrow F₁, with the result that the screw 36 can be introduced in thetapping 26 only at the end of slide of the clement 30 on the component20 in the direction of arrow F₁.

In this way, the screw 36 serves solely for blocking the element 30 inposition on the component 20 and can be tightened only once a correctposition of the element 30 on the component 20 has been attained. Therisks of the screw 36 being tightened askew in the tapping 26 are thusavoided.

In addition, the mechanical strength of the assembly formed by theelements 20 and 30 in the configuration of FIG. 3 is much greater thanthat able to be obtained with the prosthesis known from EP-A-1 051 954as, once the screw 36 is tightened, the element 30 is immobilized withrespect to the component 20 on its two sides.

In effect, the nose 25 is provided in the vicinity of a first edge 20aof the component 20 and of the surface S₂, while the tapping 26 isprovided near the opposite edge 20b of this component. In the same way,elements 35 and 37 are respectively provided in the vicinity of the twoopposite edges 30a and 30b of the element 30 and of the surface S₃.

In other words, the function of guiding of the element 30 with respectto the component 20 is obtained in the vicinity of the edges 20a and 30aof these members, while the function of blocking is obtained in thevicinity of the edges 20b and 30b.

The housing 37 is formed by a circular orifice 37a made in the metalcasing 32 for the passage of the shank of the screw 36, as well as by aconcave zone 37b made in an end part of the lining 33, in the vicinityof the edge 30b.

The head 36a of the screw 36 presents a non-circular external section asit is equipped with peripheral catching elements or teeth 36b providedto engage superficially in the inner radial surface 37c of the concavezone 37b, this contributing to the immobilization of the screw 36 inrotation and thus ensures an efficient blocking of the element 30 on thecomponent 20.

In addition, a tab 38 extends the casing 32 in the vicinity of thehousing 37, this tab being able to be folded into abutment against thehead 36a of the screw 36 when the latter is tightened, in the directionof arrow F₃ in FIG. 3, so that it performs a function of non-return forthis screw, this also contributing to the efficient blocking of theelement 30 on the component 20.

According to a variant embodiment of the invention (not shown), the head36a may present a polygonal profile, for example hexagonal or octagonal,with planar faces. In that case, the width of the tab 38 is chosen to beless than the width of the lateral faces of this head, this allowing thescrew 36 to be blocked in rotation by surface abutment of one of thesefaces against this tab.

When the element 30 is mounted on the component 20, the assembly thusproduced may pivot about axis X₁ and the joining of surfaces S₂ and S₃surrounds the surface S₁ over 360°.

A radial component adapted to be mounted on the radius R isadvantageously provided in the prosthesis according to the invention,this component 40 defining a surface intended to cooperate with thesurface S₄. However, this is not compulsory.

The invention is not limited to the sole form of embodiment represented.In particular, it may concern a prosthesis in which the projectingelement, such as the nose 25, is provided on the element 30, while astructure of fork type is provided on the ulnar component. Similarly,the tapping for receiving the blocking screw may be provided on thelocking element, the ulnar component in that case defining a housing forreceiving the locking screw.

Any mechanical means for blocking the locking element on the ulnarcomponent may be envisaged within the framework of the presentinvention.

1. Elbow prosthesis comprising a humeral component, forming a firstarticulating surface, and an ulnar component forming a secondarticulating surface adapted to be disposed around a part of said thefirst articulating surface and to pivot about a longitudinal axis ofsaid the first articulating surface, said the ulnar component beingprovided with means for mounting a locking element which forms a thirdarticulating surface extending said the second articulating surface andadapted likewise to be disposed around a part of said the firstarticulating surface, wherein said the mounting means comprise guidingmeans adapted to cooperate with complementary means provided on said thelocking element in order to guide said the locking element intranslation with respect to said the ulnar component, up to a positionwhere blocking means provided respectively on said the locking elementand on said the ulnar component may be employed to immobilize said thelocking element on said the ulnar component, said the blocking meansbeing able to be employed only in this position.
 2. The prosthesis ofclaim 1, wherein said the blocking means comprise comprises a screw anda complementary tapping provided respectively on said the lockingelement and on said the ulnar component, or vice versa, the direction ofrelative translation between said the locking element and said the ulnarcomponent as imposed by said the guiding means being non-parallel to thelongitudinal axis of said the tapping and/or of said the screw.
 3. Theprosthesis of claim 1, wherein said the guiding means comprise comprisesat least one element in relief projecting with respect to a principalpart of said the ulnar component, while the complementary means providedon said the locking element are adapted to interact with said thelocking element in relief by cooperation of shapes.
 4. The prosthesis ofclaim 3, wherein said the locking element in relief is a nose, whilesaid the complementary means comprise comprises a fork of which twobranches define therebetween a volume for receiving and for slide ofsaid sliding the nose.
 5. The prosthesis of claim 1, wherein said theguiding means and said the blocking means are arranged in the vicinityof two opposite edges of said the second articulating surface, whilesaid the complementary means and the blocking means provided on said thelocking element are arranged on two opposite edges of said the lockingelement.
 6. The prosthesis of claim 1, wherein said the blocking meanscomprise comprises a screw and a tapping, which are complementary andrespectively provided on said the locking element and on said the ulnarcomponent, or vice versa, and means are provided for blocking said thescrew in rotation.
 7. The prosthesis of claim 6, wherein the pieceagainst which the head of said screw bears, is provided with a tabfoldable into configuration of blocking of said head.
 8. The prosthesisof claim 7, wherein the head of said screw is of polygonal profile, withfaces whose width is greater than the width of said foldable tab.
 9. Theprosthesis of claim 6, wherein the head of said screw is of non-circularsection, while the piece against which said head bears, forms a spacefor receiving said head, with contact between the surface of said pieceand the outer surface of said head.
 10. The prosthesis of claim 9,wherein said head is provided with catch elements adapted to penetratesuperficially in the surface of said piece.
 11. The prosthesis of claim6, wherein when a head of the screw bears against the ulnar component,the ulnar component is provided with a tab foldable into a configurationcapable of blocking the head, and wherein when the head of the screwbears against the locking element, the locking element component isprovided with a tab foldable into a configuration capable of blockingthe head.
 12. The prosthesis of claim 11, wherein a head of the screwhas a polygonal profile having faces with widths greater than a width ofthe tab.
 13. The prosthesis of claim 6, wherein a head of the screw isof non-circular section, wherein when the head of the screw bearsagainst the ulnar component, the ulnar component forms a space forreceiving the head with contact between a surface of the ulnar componentand an outer surface of the head and wherein when the head of the screwbears against the locking element, the locking element forms a space forreceiving the head with contact between a surface of the locking elementand an outer surface of the head.
 14. The prosthesis of claim 6, whereina head of the screw is provided with catch elements adapted to penetratesuperficially in the surface of either the ulnar component or thelocking element, whichever the head bears against.
 15. An elbowprosthesis comprising: a humeral component comprising a firstarticulating surface having a curved and concave generatrix and a firstlongitudinal axis; an ulnar component comprising a first guide portionand a second articulating surface adapted to be disposed around aportion of the first articulating surface and to pivot about the firstlongitudinal axis; a locking element comprising a second guide portionand a third articulating surface that extends an arc length of thesecond articulating surface and is adapted to extend around a portion ofthe first articulating surface, the first and second guide portions ofthe ulnar component and the locking element, respectively, forming acomplementary guide structure including an extension adapted to beslidingly received within a projecting element in a complementary fitsuch that the complementary guide structure imposes sliding translationof the locking element relative to the ulnar component along a directionof slide; and a fastening structure adapted to immobilize the lockingelement with respect to the ulnar component when the locking element andthe ulnar component are engaged.
 16. The elbow prosthesis of claim 15wherein the first articulating surface comprises a component attached toa humeral stem.
 17. The elbow prosthesis of claim 15 wherein the humeralcomponent comprises: a stem adapted to be inserted in a medullary canalof a humerus; and a member adapted to abut against an external surfaceof the humerus.
 18. The elbow prosthesis of claim 15 wherein the secondand third articulating surfaces comprise similar cross-sectionalprofiles.
 19. The elbow prosthesis of claim 15 wherein the second andthird articulating surfaces comprise low-friction linings.
 20. The elbowprosthesis of claim 15 wherein the second and third articulatingsurfaces comprise a material adapted to engage a first articulatingsurface, wherein the first articulating surface is formed of metal. 21.The elbow prosthesis of claim 15 wherein the second and thirdarticulating surfaces combine to surround the first articulatingsurface.
 22. The elbow prosthesis of claim 15 wherein the guidestructure translates the locking element relative to the ulnarcomponent.
 23. The elbow prosthesis of claim 15 wherein the guidestructure comprises a direction of assembly that is non-parallel to alongitudinal axis of the fastening structure.
 24. The elbow prosthesisof claim 15 wherein the locking element and the ulnar component areengaged when the second articulating surface abuts with the thirdarticulating surface.
 25. The elbow prosthesis of claim 15 wherein thefirst guide portion of the ulnar component is located at a first edge ofthe second articulating surface and at least a portion of the fasteningstructure is located at a second edge of the second articulatingsurface.
 26. The elbow prosthesis of claim 15 wherein the fasteningstructure comprises a first hole in the locking member that is alignedwith a second hole in the ulnar component only when the locking memberis in the engaged position.
 27. The elbow prosthesis of claim 11comprising a member adapted to prevent rotation of a fastener in thefastening structure once the locking element is in the engaged position.28. An elbow prosthesis comprising: a humeral component comprising afirst articulating surface having a curved and concave generatrix and afirst longitudinal axis; an ulnar component comprising a guide elementand a second articulating surface adapted to be disposed around a partof the first articulating surface and to pivot about the longitudinalaxis; a locking element comprising a nose and a third articulatingsurface that extends an arc length of the second articulating surfaceand is adapted to extend around a portion of the first articulatingsurface, the nose being complementary to the guide element such that theguide element is adapted to slidingly receive the nose within the guideelement and impose sliding translation of the locking element along adirection of slide relative to the ulnar component; and a fasteningstructure adapted to immobilize the locking element with respect to theulnar component.
 29. An elbow prosthesis comprising: a humeral componentcomprising a first concave articulating surface with a firstlongitudinal axis; an ulnar component comprising a second articulatingsurface adapted to be disposed around a part of the first concavearticulating surface and to pivot about the longitudinal axis, the ulnarcomponent comprising at least one hole adapted to receive a fastener; alocking element comprising a third articulating surface that extends anarc length of the second articulating surface and is adapted to extendaround a portion of the first articulating surface, the locking elementcomprising at least one hole adapted to receive a fastener; and a guidestructure comprising a projecting element and an extension adapted to bereceived within the projecting element in a complementary fit to imposea direction of slide of the locking element relative to the ulnarcomponent, wherein the projecting element is located on one of the ulnarcomponent and the locking element and the extension is located on theother of the ulnar component and the locking element, and furtherwherein the hole in the locking member is substantially aligned with ahole in the ulnar component only when the locking member is fullyengaged with the ulnar component.
 30. An elbow prosthesis comprising: ahumeral component comprising a first curved articulating surfaceincluding a first longitudinal axis; an ulnar component comprising asecond articulating surface adapted to be disposed around a portion ofthe first curved articulating surface and to pivot about thelongitudinal axis; a locking element comprising a third articulatingsurface that extends an arc length of the second articulating surfaceand is adapted to extend around a portion of the first articulatingsurface; a guide structure comprising a nose and a fork adapted toreceive the nose within the fork to impose a direction of slide betweenthe ulnar component and the locking element, wherein one of the nose andthe fork is located on the ulnar component and the other of the nose andthe fork is located on the locking element; and a fastening structureadapted to immobilize the locking element with respect to the ulnarcomponent, wherein the guide structure comprises a direction of assemblythat is non-parallel to a longitudinal axis of the fastening structure.